Abstract: The dynamic characteristics of earthquake and structure response can be reflected precisely by the theory of response spectrum. A dynamic can be changed into a static when the theory of response spectrum is used to do the aseismic design of a structure. However it is difficult to conduct the aseismic designs of modern and large complicated structures with long spans, and deal with non proportional damping etc. Using power spectrum based on pseudo excitation method can solve the above problems and save time. Meanwhile the computing errors can also be avoided during the process of solutions.